The present invention relates generally to relational database technology, and more specifically, to improved input/output (I/O) efficiency for online analysis processing in a relational database.
A relational database management system (RDBMS) or “relational model” was introduced in the 1970s as a system for enabling interaction of data in various tables through formal algebraic and descriptive query language using structured query language (SQL).
In general, data is stored in a RDBMS in tables in accordance with a relationship storage model. The data is stored in the table as a set of sequences of rows in a data storage mechanism (for example, a disk, a main memory, other memories, etc.). In some systems an index is created as an additional data structure, which enables rapid access to data in specific row(s).
A SQL query is used in two categories of database interactive applications: an OLTP (Online Transaction Process) and an OLAP (Online Analysis Process). An OLTP application deals with online transaction processes and adopts a traditional row-stored solution. Information related to an OLTP transaction may be effectively added to, or retrieved from, a single table of a relational database. In the case of the OLAP, using small databases with simple relationships, a request of the OLAP application for the information can be responded to with reasonable efficiency using the row-based storage scheme. However, in the more complicated case of a query of a multi-dimensional database in an OLAP application that involves the search of only a few columns in a table consisting of many rows, and retrieval of aggregated data from those rows, if a row-based storage scheme is still used, then each of the tables is scanned across all dimensions, even those for which no scan is required, resulting in low I/O efficiency of the row-based storage scheme in the OLAP application.